How Best to Coerce Python Objects to Integers?

Erik python at
Tue Jan 3 07:22:16 EST 2017

On 03/01/17 22:47, Chris Angelico wrote:
> On Wed, Jan 4, 2017 at 9:42 AM, Ethan Furman <ethan at> wrote:
>> Aside from calling "except Exception" a "naked except"
> If you read the comments, you'll see that he originally had an actual
> bare except clause, but then improved the code somewhat in response to
> a recommendation that SystemExit etc not be caught.

But, as stated at the top of the article, his brief was: "The strings come from 
a file that a human has typed in, so even though most of the values are good, a 
few will have errors ('25C') that int() will reject.".

What he *should* have done is just validated his input strings before 
presenting the string to int() - i.e., process the input with knowledge that is 
specific to the problem domain before calling the general-purpose function.

He mentions temperature sensors, so perhaps stripping a trailing 'c' or
'C' is a reasonable thing to do (or even, if there's a trailing 'f' or
'F', performing a numerical conversion after the value is known).

Instead, he tried to patch around int() rejecting the strings. And then decided 
that he'd patch around int() rejecting things that weren't even strings even 
though that's not what the function has (apparently) been specified to receive.

The "bulletproof" result will convert "25C" to None even though 25 is probably 
a reasonable result for that string in his domain problem domain.


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